Snap-on lock for turbomachinery blades

ABSTRACT

A snap-on lock for turbomachinery blade including a spring snapon member shaped to engage a circumferential slot in the blade root and to overlap the disc surface when so engaged and to further frictionally engage the side surfaces of the blade root so as to prevent axial movement of the blade within the disc retaining slot and which will be acted upon by centrifugal force to be more securely retained in the blade root circumferential slot.

United States Patent [191 Bergmann 1 SNAP-ON LOCK FOR TURBOMACHINERYBLADES [75] Inventor: Richard J. Bergmann, Vernon,

Conn.

[73] Assignee: United Aircraft Corporation, East Hartford, Conn.

[451 Oct. 15, 1974 2,994,507 8/1961 Keller et a1. 416/221 3,008 68911/1961 Morley et a1. 416/221 3,341,174 9/1967 Manning 416/220 PrimaryExaminer-Everette A. Powell, Jr. Attorney, Agent, or Firm-Vernon F.Hauschild [5 7 ABSTRACT A snap-on lock for turbomachinery bladeincluding a spring snap-on member shaped to engage a circumferentialslot in the blade root and to overlap the disc surface when so engagedand to further frictionally engage the side surfaces of the blade rootso as to prevent axial movement of the blade within the disc retainingslot and which will be acted upon by centrifugal force to be moresecurely retained in the blade root circumferential slot.

11 Claims, 9 Drawing Figures PATENIEUDET 151914 sum 10? 2 F/6.Z F//SNAP-ON LOQK FOR TURBOMACHINERY BLADES BACKGROUND OF THE INVENTION 1.Field of Invention This invention relates to the retention of removableblades in discs of turbomachinery and particularly to retainingmechanism which is flexible and which may be snapped into position and,further, which is urged into proper position by centrifugal force duringrotation of the rotor.

2. Description of the Prior Art The blade retaining prior art includesmany mechanisms such as Manning U.S. Pat. No. 3,341,174; Keller et al.U.S. Pat. No. 2,994,507; Hill U.S. Pat. No. 2,755,062; Newton et al.U.S. Pat. No. 2,865,076; and Pancoe U.S. Pat. No. 1,949,027, most ofwhich require special machining of the blade and/or disc to performtheir retaining functions but none of which are of the snap-on varietyand operable to be retained in locking position by centrifugal force.

Other prior art utilizes a tablock which is fitted between the discs andthe blade at the bottom of the disc blade retaining slot and in whichblade locking is accomplished by deforming the ears of the tablock atthe front and rear interface of the disc and blade. This tablockmechanism sometimes results in improperly locked parts and tablock earsare prone to crack off in usage or upon blade replacement.

SUMMARY OF THE INVENTION A primary object of the present invention is toprovide a blade retaining mechanism which locks the blade in the disc,which is capable of being installed with a minimum of effort, which maybe readily removed, which is reusable, which is durable, and which isinexpensive to produce.

It is still a further object of the present invention to teach such ablade lock which operates by a snap-on action to perform a blade lockingfunction and which is acted upon by centrifugal force to retain the lockin position.

It is still a further object of the present invention to teach such asnap-on lock shaped to be positioned in a circumferentially extendingslot in the blade root while overlapping the disc rim and frictionallyengaging the blade root to retain the lock in position.

It is still a further object of the present invention to teach such ablade lock which may be used either at one axial end of a blade incombination with any other type of blade axially retainer at theopposite bladeend or which may be used at both ends of the blade.

It is a further object of the present invention to teach such a bladelock which does not interfere with the installation of the blade in thedisc, which does not require special machining of the disc, and whichis'of generally of U-shape cross section and fabricated of spring rodmaterial to be snapped over circumferentially extending projections onthe blade root, and into position into a circumferentially extendingslot in the blade root and, while overlapping the disc rim to therebyretain the blade in position.

It is a further object of the present invention to teach a modified formof this blade lock which requires minimal machining of the disc andblade and which utilizes the same snap-on lock member as in thepreferred embodiment. In this construction, a retainer mechanism isshaped to be received matingly in an axially extending slot in the baseof the blade so as to thereby be positioned when assembled between thedisc and the blade. The retainer mechanism extends beyond the discretainer slot with the blade root and includes circumferentiallyextending recesses in opposite sides thereof which are aligned whenassembled with the circumferential slot in the blade root so that thesnap-on lock of my invention is received both in the circumferentiallyextending recesses of the retainer mechanism and the circumferentialslot of the blade root so as to lock the blade in axial position whenthe snap-lock member is so engaged and overlaps the disc radialsurfaces. The retainer mechanism also preferably is shaped to include aretainer lug at the opposite end from its circumferential recesses whichis shaped to engage the other radial surface of the disc to preventblade axial motion in the direction opposite to that being restrained bythe snapon lock member.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a showing of aturbomachinery rotor with a support disc having peripheral bladesextending therefrom.

FIG, 2 is a partial, enlarged showing of a blade assembled in the disc,and showing my blade lock system as sembled.

FIG. 3 is a showing through line 3-3 of FIG. 2.

FIG. 4 is a partial showing of the blade-to-disc connection toillustrate my lock retaining slot with the lock member removedtherefrom.

FIG. 5 is a partial showing of the disc to illustrate the bladeretaining slot shape.

FIG. 6 is a showing of a blade root to illustrate its cross-sectionalshape.

FIG. 7 is a Figure corresponding to FIG. 1 of a modified form of myinvention.

FIG. 8 is a view taken along section line 8-8 of FIG. 7.

FIG. 9 is a view taken along section line 99 of FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 we see atypical turbomachinery rotor 10 which includes a structural disc 12which is concentric about and adapted to be mounted about for rotationabout axis 14 and which further includes a plurality of blades 16attached to the outer periphery thereof for rotation therewith aboutaxis 14. The construction of turbomachinery rotors of the type which maybe used in turbines or compressors or free turbines driven by fluids,such as steam or gas, is very well known and will not be described inany further detail herein. For a more complete description ofaconstruction of a turbomachinery rotor, reference is hereby made toU.S. Pats. Nos. 2,711,631 and 2,747,367.

Now referring to FIGS. 2 through 4', we see a blade 16 projecting fromdisc 12 and while a single blade is illustrated, it should'be borne inmind that in conventional fashion there are a plurality of such radially'extending blades positioned in spaced circumferential relationshipabout the periphery of disc 12. Disc 12 comprises a central web member18 which supports rim 20. Rim 20 extends circumferentially about theperiphery of disc 12 and may include circumferential flange members 22and 24 which serve to cooperate with adjacent members (not shown) forgas sealing and other purposes. Rim 20 includes substantially radiallyand circumferentially extending surface 26 at its axially forward endand substantially radially and circumferentially extending surface 28 atits axially after end.

As best shown in FIG. 5, rim 20 includes a plurality of blade retainingslots 31), one for each blade, which may extend axially through rim 20or at an angle to the axis, as desired, to properly position blades 16with respect to cooperating apparatus (not shown) and as used herein theterms axially extending" and axial means either of these arrangements.Disc slot 30 and blade root 44, of course, extend in the same direction.

Disc slot 30 includes a mushroomed or circumferentially expanded portion32 at the radially inner end thereof and converging surfaces 34 and 36extending between mushroomed portion 32 and substantially radiallyextending surfaces 38 and 40 thereof. While FIG. discloses a preferredcross-sectional shape of blade retaining disc slot 30, it will beevident to those skilled in the art that any suitable slot shape toretain blades 16 radially in disc 12 against the operation ofcentrifugal force during rotation of the rotor may be utilized with myinvention.

Blade 16 includes an airfoil portion 42 (see FIG. 2) positioned betweenthe blade root 44 and the blade tip (not shown). Blade root 44 is shapedselectively in cross section as best shown in FIG. 3 to matingly bereceived in and engage disc slot 30 so as to secure blade 16 in radialposition during rotor rotation.

As best shown in FIG. 6, blade root 44 includes a bulbous or mushroomedshape radially inner end or base 46 which extends circumferentially whenthe blade is inserted into the disc and further includes substantiallyradially extending side surfaces 48 and 50 together with convergingsurfaces 52 and 54 positioned therebetween. It will be noted that incross section blade root 44 is substantially the same shape as disc slot30 so that the blade may be inserted into the disc for support therefromby axially inserting blade root portions 44 into disc slot 30 commencingat one of the rim lateral surfaces 26 and proceeding toward the other28. In the preferred embodiment disclosed herein, the bladeroot 44commences to be axially inserted into disc slot 30 at disc surface 26and is moved within the slot toward disc surface 28 until the blade 16reaches its FIG. 2 fully inserted position wherein substantiallyradially extending surface 56 of blade stop tab 58 abuts disc surface 26to prevent further movement of blade 16 toward disc surface 28.

At the opposite end of blade root 14 from stop 58 is retainingslotdefming mechanism 60 which is preferably an integral extension ofroot 44, as is stop 58. Slot 62 extends through slot defining mechanism60 and, with the blade assembled onto the disc as best shown in FIGS. 2and-3, slot 62 is circumferentially extending and includes a first wall64 (see FIG. 4) which is in radial alignment with rim surface 28 and asecond wall 66 spaced axially therefrom to define the slot axialdimension a therebetween. Preferably, slot 62 is a straight slot whichis machined in any convenient fashion, such as grinding, milling orchemically, in root 44 of each blade 16. When the blades 16 areassembled disc 12, the slots 62 extend in a substantiallycircumferential direction and are so described herein, althought itshould be borne in mind that the slot is preferably straight, as opposedto curved.

By viewing FIG. 3, it will be noted that slot 62, at the FIG. 3 station,cuts into blade root bulbous end 46 up to the point of the slot base 68so that circumferentially extending projections 70 and 72 are located inblade root 44 between slot base 68 and blade side surfaces 48 and 50. I

As best shown in FIGS. 2 and 3, snap-on lock member 74, which is ofgenerally U-shaped cross section, is snapped over circumferentialprojections 70 and 72 and into retaining slot 62 such that it is snuglyreceived in slot 62 since its axial dimension and the axially dimensiona of the slot 62 are substantially the same and bears against both slotsurface 64 and rim surface 28, as well as slot surface 66, so as toprevent blade 16 from moving toward rim surface 26 and therebycooperates with positive stop member 58 to position blade 16 in axialposition. As best shown in FIG. 3, snap-on lock member 74, which ispreferably made of spring steel and in rod form, includes a first loop76 which projects radially inwardly from slot 62 to overlap and abut rimsurface 28, further includes circumferentially outwardly extending loops78 and 80, which envelop circumferential projections 70 and72,-respectively, and still further includes circumferentially inwardlydirected loops 82 and 84, which frictionally engage blade root sidesurfaces 48 and 50, respectively, since their unsprung circumferentialspacing is less than the circumferential spacing between blade rootsurfaces 48 and 50. In view of the fact that slot 62 is radiallyinwardly directed, and because snap-on lock member 74 has its open endpositioned in a radially outwardly direction, centrifugal force will actduring rotor rotation to impose a retaining force upon lock 74 and willserve to hold straight portions 86 and 88 thereof firmly against thebase 68 of slot 62.

As best shown in FIG. 3, it should'be noted that both lock member 74,blade root 44, and disc slot 30 are symmetric about radial line 90 whichpasses through the midcircumferential position of disc slot 30.

FIGS. 7-9 show another embodiment of my blade lock which is generallysimilar in all respects to the embodiment shown in FIGS. 1-6 except thata retainer member is positioned in an axially extending slot in the baseof the blade root, which retainer member has circumferentially extendingrecesses which are aligned with the circumferentially extending bladeroot slot so as to receive the snap-on lock member and cooperatetherewith in preventing blade axial motion in a first direction andincluding a projection at its opposite end which prevents bladeaxialmovement in the opposite direction. In describing the specifics ofthe FIG. 7-9 embodiment, the same reference numerals will be used todescribe parts which correspond to FIGS. 1-6 embodiment but in primedform. In FIG. 7-9 embodiment,

blade root section 44' includes axially extending slots opening onto thebase 102 thereof. Lock retainer 104 is received in slot 100 and shapedto matingly engage slot 100. Projection 106 extends from one end ofretainer 104 and is shaped so that radially extending surface 108thereof engages radial surface 26' of disc 12' to prevent axial motionof retainer 104 in a first axial direction. Retainer 104 extends beyonddisc surface 28 in the same fashion as slot defining mechanism 60 and isshaped to have circumferentially extending recesses 110 and 112extending in alignment toward each other from the oppositecircumferential surfaces 114 and 116, respectively, of retainer 104.Recesses 110 and 112 align with blade root circumferentially extendingslots 62' and are of selected axial dimension so as to snugly receivesnapon lock member 74, which now engages recesses 110 and 112 as well ascircumferential slot 62' and continues to overlap and abut disc radialsurface 28'. In all other respects the FIG. 7-9.

embodiment is similar to the FIG. 1-6 embodiment.

It will therefore be seen that my constructions lock blades 16 onto disc12 in such a way that each blade is radially, circumferentially andaxially retained. In addition, my snap-on blade lock 74 is bothfrictionally engaged in position by its own resiliency but is also aidedby centrifugal force during rotor rotation to remain in position.Further, my lock member 74 can be used either at one end of the bladeroot 44 withany other type of blade axial retainer at the opposite end,or at both ends of the blade root 44 if it is desired to have aconstruction in which the blades can be inserted and removed from eitheraxial side of the disc. Further, my snap-on lock member 74 isinexpensive to manufacture, is durable, is easily assembled into theblade-disc combination, is easily withdrawn therefrom and replaced, andis reusable.

I wish it to be understood that I do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

I claim:

I. A turbomachinery rotor including in combination:

A. a support disc member concentric about an axis and having:

l. a rim portion extending circumferentially around the outer peripheryof said disc member and having substantially radial surfaces at theaxial ends thereof,

2. a plurality of substantially axially extending and circumferentiallyspaced disc slots in said disc rim portion and extending for the fullaxial dimension of the rimmed portion and opening into said radialsurfaces and being of selected crosssectional shape to be greater incircumferential dimension at a station nearer the axis than at a stationfarther from the axis,

B. a plurality of blade members each received in one of said disc slotsand having:

1. a root section of substantially the same axial dimension as said discrim portion so that the axial ends of each blade root section sopositioned in its disc slot will substantially align with the rimportion radial surfaces and being of selected cross-sectional shape soas to be matingly received in said disc slot to prevent radial movementof the blade relative to the disc member and having circumferentiallyspaced side surfaces when so positioned in its disc slot,

C. stop means operative to prevent said blade member from moving in afirst axial direction within said disc slot,

D. a retaining slot defining member located at an axial end of the bladeroot section and shaped to define a substantially circumferentiallyextending retaining slot opening toward the axis and being of selectedaxial dimension and having a first wall thereof extending substantiallyradially and in alignment with the rim portion radial surface at thatradial end of the disc rim portion and having a second wall in selectedaxial spaced relation to the first wall to define the retaining slotaxial dimension therebetween, and further being shaped to definecircumferential projections radially outward of the slot,

E. a snap-on lock member shaped to snap over said circumferentialprojections and to be wedged into said retaining slot and to abuttinglyengage the disc radial surface so as to prevent movement of the bladewithin the disc slot in an axial direction opposite to said first axialdirection and so that centrifugal force will apply a retaining force onthe snap-on lock member in said retaining slot during rotor rotation.

2. A rotor according to claim 1 wherein said stop means is attached toone end of said root section and is shaped topresent a substantiallyradially extending surface dimensioned to abut the disc rim radialsurface when the blade root section is so inserted into said disc slotto prevent further movement of the blade in the direction of insertion.

3. A rotor according to claim 1 wherein said disc slot and said bladeroot section are shaped in cross section to be symmetric about aradially extending line extending through the circumferential midpointthereof and to mushroom circumferentially at their radially inner endsand to present converging surfaces extending between the mushroomportion and for a selected radial distance outwardly thereof to provideabutting bladeto-disc blade retention surfaces in opposition tocentrifugal force, and wherein said retaining slot'extendscircumferentially in said mushroom portion of said blade root sectionand terminates at its outer radial end radially inwardly of said rootsection side surfaces so that the blade root section presentscircumferentially extending projections at the station of the retainingslot projecting circumferentially from opposite circumferential sides ofthe blade root section side surfaces.

4. A rotor according to claim 3 wherein said snap-on lock is aspring-rod member shaped to snap over said blade root sectioncircumferential projections and into said blade root section retainingslot, and is further shaped to project over and abut said rim portionradial surfaces and further to engage the base of said retaining slotand to engage the side surfaces of said root section.

5. A rotor according to claim 4 wherein said snap-on lock member isshaped to include a first loop which overlaps one of the radial surfacesof the rim portion of the disc, two circumferentially outwardlyextending loops which overlap the blade root section circumferentialprojections, and two circumferentially inwardly directed loops whichhave less unsprung circumferential separation that the circumferentialseparation between said blade root section side surfaces and which snapover said root section circumferential projections and whichfrictionally engage the blade root section side surfaces.

6. A rotor according to claim 5 wherein said snap-on lock member isconcentric about a radially extending line extending through themid-circumferential station of said blade root portion when so snappedinto position and including straight sections on opposite sides of saidradial line engaging the retaining slot base.

7. A turbomachinery rotor including:

A. a disc having an axis and adapted to be mounted for rotationthereabout,

B. a plurality of vanes adapted to be connected to the outer peripheryof the disc,

C. dovetail connecting means connecting each blade to the disc peripheryso as to position the blades circumferentially on the disc to beradially extending and restrained during rotation and so as to permitaxial movement of the blade into position and for disassembly from thedisc when unrestrained, and

D. blade axial retention means including:

1. stop means operative to prevent the blade from moving'in a firstaxial direction within the disc,

2. means defining a circumferentially extending slot in the blade rootin alignment with the disc surface adjacent that end of the root andincluding circumferentially extending projections at the base of thecircumferential slot, and

3. snap-on lock means shaped to snap over said circumferentialprojections and to frictionally engage the sides of the blade root andto be snugly received into said circumferential slot and so as to bemore firmly retained in said slot in response to the centrifugal forcegenerated by disc rotation and, further, to overlap the disc surface soaligned with the slot.

8. A turbomachinery rotor including in combination:

A. a support disc member concentric about an axis and having:

1. a rim portion extending circumferentially around the outer peripheryof said disc member and having substantially radial surfaces at theaxial ends thereof, a plurality of substantially axially extending andcircumferentially spaced disc slots in said disc rim portion andextending for the full axial dimension of the rimmed portion and openinginto said radial surfaces and being of selected crosssectional shape tobe greater in-circumferential dimension at a slot base station nearerthe axis than at a station farther from the axis,

B. a plurality of blade members each received in one of said disc slotsand having:

1. a root section of substantially the same axial dimension as said discrim portion so that the axial ends of each blade root section sopositioned in its disc slot will substantially align with the rimportion radial surfaces and being of selected cross-sectional shape soas to be matingly received in said disc slot to prevent radial andcircumferential movement of the blade relative to the 'disc member andhaving circumferentially spaced side surfaces and a base adjacent thedisc slot base when so positioned in its disc slot, and further havingan axially extending slot opening into the base thereof.

C. stop means operative to prevent said blade member from moving in afirst axial direction within said disc slot,

D. a retaining slot defining member located at an axial end of the bladeroot section and shaped to define a substantially circumferentiallyextending retaining slot opening toward the axis and being of selectedaxial dimension and having a first wall thereof extending substantiallyradially and in alignment with the rim portion radial surface at thatradial end of disc rim portion and having a second wall in selectedaxial spaced relation to the first wall to define the retaining slotaxial dimension therebetween, and further being shaped to definecircumferential projections radially outward of the slot,

E. a retainer member shaped to be matingly received in the blade rootsection slot and having aligned circumferentially extending recessesprojecting toward each other from the opposite circumferentially spacedand axially extending sides thereof and positioned in alignment with thecircumferentially extending slot of the retaining slot defining member,and

F. a snap-on lock member shaped to snap over said circumferentialprojections and to be wedged into said blade root section retaining slotand said retainer member recesses and to abuttingly engage the discradial surface so as to prevent movement of the blade within the discslot in an axial direction opposite to said first axial direction and sothat centrifugal force will apply a retaining force on the snap-on lockmember in said retaining slot during rotor rotation.

9. A rotor according to claim 8 wherein the stop means is a projectionextending from the retaining member and shaped to engage the disc radialsurface opposite the disc radial surface engaged by the snap-on lockmember.

10. A turbomachinery rotor including:

A. a disc having an axis and adapted to be mounted for rotationthereabout,

B. a plurality of vanes adapted to be connected to the outer peripheryof the disc,

C. dovetail connecting means connecting each blade to the disc peripheryso as to position the blades circumferentially on the disc to beradially extending and restrained during rotation and so as to permitaxial movement of the blade into position and for disassembly from thedisc when unrestrained, and

D. blade axial retention means including:

1. stop means operative to prevent the blade from moving in a firstaxial direction within the disc,

2. means defining a circumferentially extending slot in the blade rootin alignment with the disc surface adjacent that end of the root andincluding circumferentially extending projections at the base of thecircumferential slot,

3. means defining an axially extending slot in the blade root andopening onto the base thereof, 4. a retainer member shaped to bematingly received in the blade root axial slot and having alignedcircumferentially extending recesses projecting toward each other fromthe opposite circumferentially spaced and axially extending sidesthereof and positioned in alignment with the blade rootcircumferentially extending slot,

5. snap-on lock means shaped to snap over said circumferentialprojections and to frictionally engage the sides of the blade root andto be snugly received into said blade root circumferential slot and saidretainer member recesses and so as to be more firmly retained in saidslot and recesses in response to the centrifugal force generated by discrotation and, further, to overlap the disc surface so aligned with theslot.

11. A rotor according to claim 10 wherein the stop

1. A turbomachinery rotor including in combination: A. a sUpport discmember concentric about an axis and having:
 1. a rim portion extendingcircumferentially around the outer periphery of said disc member andhaving substantially radial surfaces at the axial ends thereof,
 2. aplurality of substantially axially extending and circumferentiallyspaced disc slots in said disc rim portion and extending for the fullaxial dimension of the rimmed portion and opening into said radialsurfaces and being of selected cross-sectional shape to be greater incircumferential dimension at a station nearer the axis than at a stationfarther from the axis, B. a plurality of blade members each received inone of said disc slots and having:
 1. a root section of substantiallythe same axial dimension as said disc rim portion so that the axial endsof each blade root section so positioned in its disc slot willsubstantially align with the rim portion radial surfaces and being ofselected cross-sectional shape so as to be matingly received in saiddisc slot to prevent radial movement of the blade relative to the discmember and having circumferentially spaced side surfaces when sopositioned in its disc slot, C. stop means operative to prevent saidblade member from moving in a first axial direction within said discslot, D. a retaining slot defining member located at an axial end of theblade root section and shaped to define a substantiallycircumferentially extending retaining slot opening toward the axis andbeing of selected axial dimension and having a first wall thereofextending substantially radially and in alignment with the rim portionradial surface at that radial end of the disc rim portion and having asecond wall in selected axial spaced relation to the first wall todefine the retaining slot axial dimension therebetween, and furtherbeing shaped to define circumferential projections radially outward ofthe slot, E. a snap-on lock member shaped to snap over saidcircumferential projections and to be wedged into said retaining slotand to abuttingly engage the disc radial surface so as to preventmovement of the blade within the disc slot in an axial directionopposite to said first axial direction and so that centrifugal forcewill apply a retaining force on the snap-on lock member in saidretaining slot during rotor rotation.
 2. a plurality of substantiallyaxially extending and circumferentially spaced disc slots in said discrim portion and extending for the full axial dimension of the rimmedportion and opening into said radial surfaces and being of selectedcross-sectional shape to be greater in circumferential dimension at aslot base station nearer the axis than at a station farther from theaxis, B. a plurality of blade members each received in one of said discslots and having:
 2. means defining a circumferentially extending slotin the blade root in alignment with the disc surface adjacent that endof the root and including circumferentially extending projections at thebase of the circumferential slot,
 2. a plurality of substantiallyaxially extending and circumferentially spaced disc slots in said discrim portion and extending for the full axial dimension of the rimmedportion and opening into said radial surfaces and being of selectedcross-sectional shape to be greater in circumferential dimension at astation nearer the axis than at a station farther from the axis, B. aplurality of blade members each received in one of said disc slots andhaving:
 2. A rotor according to claim 1 wherein said stop means isattached to one end of said root section and is shaped to present asubstantially radially extending surface dimensioned to abut the discrim radial surface when the blade root section is so inserted into saiddisc slot to prevent further movement of the blade in the direction ofinsertion.
 2. means defining a circumferentially extending slot in theblade root in alignment with the disc surface adjacent that end of theroot and including circumferentially extending projections at the baseof the circumferential slot, and
 3. snap-on lock means shaped to snapover said circumferential projections and to frictionally engage thesides of the blade root and to be snugly received into saidcircumferential slot and so as to be more firmly retained in said slotin response to the centrifugal force generated by disc rotation and,further, to overlap the disc surface so aligned with the slot.
 3. Arotor according to claim 1 wherein said disc slot and said blade rootsection are shaped in cross section to be symmetric about a radiallyextending line extending through the circumferential midpoint thereofand to mushroom circumferentially at their radially inner ends and topresent converging surfaces extending between the mushroom portion andfor a selected radial distance outwardly thereof to provide abuttingblade-to-disc blade retention surfaces in opposition to centrifugalforce, and wherein said retaining slot extends circumferentially in saidmushroom portion of said blade root section and terminates at its outerradial end radially inwardly of said root section side surfaces so thatthe blade root section presents circumferentially extending projectionsat the station of the retaining slot projecting circumferentially fromopposite circumferential sides of the blade root section side surfaces.3. means defining an axially extending slot in the blade root andopening onto the base thereof,
 4. a retainer member shaped to bematingly received in the blade root axial slot and having alignedcircumferentially extending recesses projecting toward each other fromthe opposite circumferentially spaced and axially extending sidesthereof and positioned in alignment with the blade rootcircumferentially extending slot,
 4. A rotor according to claim 3wherein said snap-on lock is a spring-rod member shaped to snap oversaid blade root section circumferential projections and into said bladeroot section retaining slot, and is further shaped to project over andabut said rim portion radial surfaces and further to engage the base ofsaid retaining slot and to engage the side surfaces of said rootsection.
 5. A rOtor according to claim 4 wherein said snap-on lockmember is shaped to include a first loop which overlaps one of theradial surfaces of the rim portion of the disc, two circumferentiallyoutwardly extending loops which overlap the blade root sectioncircumferential projections, and two circumferentially inwardly directedloops which have less unsprung circumferential separation that thecircumferential separation between said blade root section side surfacesand which snap over said root section circumferential projections andwhich frictionally engage the blade root section side surfaces. 5.snap-on lock means shaped to snap over said circumferential projectionsand to frictionally engage the sides of the blade root and to be snuglyreceived into said blade root circumferential slot and said retainermember recesses and so as to be more firmly retained in said slot andrecesses in response to the centrifugal force generated by disc rotationand, further, to overlap the disc surface so aligned with the slot.
 6. Arotor according to claim 5 wherein said snap-on lock member isconcentric about a radially extending line extending through themid-circumferential station of said blade root portion when so snappedinto position and including straight sections on opposite sides of saidradial line engaging the retaining slot base.
 7. A turbomachinery rotorincluding: A. a disc having an axis and adapted to be mounted forrotation thereabout, B. a plurality of vanes adapted to be connected tothe outer periphery of the disc, C. dovetail connecting means connectingeach blade to the disc periphery so as to position the bladescircumferentially on the disc to be radially extending and restrainedduring rotation and so as to permit axial movement of the blade intoposition and for disassembly from the disc when unrestrained, and D.blade axial retention means including:
 8. A turbomachinery rotorincluding in combination: A. a support disc member concentric about anaxis and having:
 9. A rotor according to claim 8 wherein the stop meansis a projection extending from the retaining member and shaped to engagethe disc radial surface opposite the disc radial surface engaged by thesnap-on lock member.
 10. A turbomachinery rotor including: A. a dischaving an axis and adapted to be mounted for rotation thereabout, B. aplurality of vanes adapted to be connected to the outer periphery of thedisc, C. dovetail connecting means connecting each blade to the discperiphery so as to position the blades circumferentially on the disc tobe radially extending and restrained during rotation and so as to permitaxial movement of the blade into position and for disassembly from thedisc when unrestrained, and D. blade axial retention means including:11. A rotor according to claim 10 wherein the stop means is a projectionextending from the retaining member and shaped to engage the discsurface opposite the disc surface engaged by the snap-on lock member.